Score : $200$ points

问题陈述

高桥将回答 $N$ 个测验问题。 最初，他有 $X$ 分。每次他回答问题，如果回答正确，他将获得 $1$ 分；如果回答错误，他将失去 $1$ 分。 然而，有一个例外：当他有 $0$ 分时，回答错误的问题不会失去分数。

你将得到一个字符串 $S$，表示高桥的答案是否正确。 如果从左边数第 $i$ 个字符是 o，则意味着他第 $i$ 个问题的答案正确；如果那个字符是 x，则意味着他第 $i$ 个问题的答案错误。 最后他将有多少分？

以上为大语言模型 kimi 翻译，仅供参考。

Problem Statement

Takahashi will answer $N$ quiz questions.
Initially, he has $X$ points. Each time he answers a question, he gains $1$ point if his answer is correct and loses $1$ point if it is incorrect.
However, there is an exception: when he has $0$ points, he loses nothing for answering a question incorrectly.

You will be given a string $S$ representing whether Takahashi's answers are correct.
If the $i$-th character of $S$ from the left is o, it means his answer for the $i$-th question is correct; if that character is x, it means his answer for the $i$-th question is incorrect.
How many points will he have in the end?

Constraints

• $1 \le N \le 2 \times 10^5$
• $0 \le X \le 2 \times 10^5$
• $S$ is a string of length $N$ consisting of o and x.

Input

Input is given from Standard Input in the following format:

$N$ $X$

$S$

Output

Print the number of points Takahashi will have in the end.

Sample Input 1

3 0
xox

Sample Output 1

0

Initially, he has $0$ points.
He answers the first question incorrectly but loses nothing because he has no point.
Then, he answers the second question correctly, gains $1$ point, and now has $1$ point.
Finally, he answers the third question incorrectly, loses $1$ point, and now has $0$ points.
Thus, he has $0$ points in the end. We should print $0$.

Sample Input 2

20 199999
oooooooooxoooooooooo

Sample Output 2

200017

Sample Input 3

20 10
xxxxxxxxxxxxxxxxxxxx

Sample Output 3

0